1. Field
This disclosure relates to multimode seekers that incorporate both radio frequency and imaging infrared sensors.
2. Description of the Related Art
Weapon systems may include a variety of imaging or non-imagining sensors to detect and track potential targets. Sensors used to guide missiles to an intended target are commonly referred to as seekers. Seekers may operate in various portions of the electromagnetic spectrum, including the visible, infrared (IR), microwave, and millimeter wave (MMW) portions of the spectrum. Some missiles may incorporate multiple sensors that operate in more than one portion of the spectrum. A seeker that incorporates multiple sensors that share a common aperture and/or common optical system is commonly called a multimode seeker.
Seekers operating in the infrared portion of the electromagnetic spectrum commonly use reflective or catadioptric (containing both reflective and refractive elements) imaging optical systems. The function of the imaging optical system is to form an image of a distant scene on a detector such as a focal plane array. Such seekers may be susceptible to stray light that may illuminate the detector and degrade the contrast or dynamic range of the image. For example, sunlight illuminating the detector may completely wash out the image of the scene formed by the imaging optical system. Thus infrared seekers may contain baffles or other mechanisms to prevent stray light from impinging on the detector. These baffles may be, for example, thin metal shields placed judiciously within the imaging optical system.
A multimode seeker system may include an imaging infrared (BR) sensor and, for example, a MMW sensor that share a common aperture and at least some elements of a reflective or catadioptric optical system. Metal stray light baffles generally cannot be used in a multimode MMW/IIR seeker since metal baffles may degrade the performance of the MMW sensor.
Throughout this description, elements appearing in figures other than flow charts are assigned three-digit reference designators, where the most significant digit is the figure number and the two least significant digits are specific to the element. An element that is not described in conjunction with a figure may be presumed to have the same characteristics and function as a previously-described element having a reference designator with the same least significant digits.